This invention relates in general to integrated lead suspensions for hard disk drives and in particular to fabricating and applying non-homogenous laminate materials to integrated lead suspensions with ESD shunting.
In hard disk drive manufacturing, one type of head gimbal assembly has an integrated lead suspension (ILS). An ILS is typically formed by laminating several layers of material together and then selectively etching the layers to achieve a desired architecture. Alternatively, the layers may be formed by plating them on top of one another. These layers usually comprise at least one of each of the following: a stainless steel substrate or support layer, an insulation layer such as a polyimide, and a conductor layer such as copper. An ILS with a bent lead type design must be etched on both sides to clear the polyimide on the bent lead. This step requires additional process time and adds cost to the suspension.
In an ILS, the conductors carry the electrical signals from the read/write heads to a flexible cable. The polarity of the signals at the heads determines the polarity of the termination pads at the flexible cable since the conductors cannot cross over one another. This is a serious problem if multiple heads with different polarities must be connected to the same flexible cable which has only one set of polarities.
In addition, some sliders are especially sensitive to electrostatic discharge (ESD). One example is the giant magneto resistive (GMR) head, which can be easily damaged by an ESD event. ESD damage lowers manufacturing yield and increases the cost of the head gimbal assembly. Improved methods for manufacturing integrated lead suspensions are needed to address these issues.
An integrated lead suspension is formed from a laminate of three materials in a variety of configurations having from three to five layers. The materials are stainless steel, polyimide and copper. Each layer is essentially homogeneous, but may be formed with one or more holes or voids prior to the formation of the laminate. The voids allow dielectric material to be removed from the area beneath the conductors to simplify processing and reduce the cost of the suspensions. The voids can also form a window through which conductors can be shorted to other conductive layers to form an electrostatic discharge shunt Alternatively, the shorting of conductors can be used as a cross-over for various conductors.